1. Field of the Invention
The present invention relates to a method of fabricating a leadframe used in a semiconductor assembly process, and more particularly, to a method of fabricating a leadframe with inner leads having a fine pitch.
2. Description of the Related Art
A lead frame is an essential component of a semiconductor package because it connects the package to external devices and supports a semiconductor chip. The lead frame includes a chip pad for mounting a chip, an inner lead, and an external lead. There are two currently-known lead frame manufacturing methods, a stamping method and an etching method. In a stamping method, a sequential transfer-type molding machine transfers a lead frame material sequentially and presses it to manufacture a product in a predetermined shape. This method is usually employed in the mass production. In an etching method, a lead frame material is coated with a photoresist and undergoes photolithography, whereby a lead frame is manufactured by a chemical etch reaction. The etching is generally used during the initial development of a lead frame with a fine pattern. With the recent reduction in semiconductor chip size, a lead frame fabrication technique has been developed to achieve a lead frame with a finer pattern. For a lead frame fabricated by the stamping method, if the chip size is reduced, the lead frame design should be changed. Specifically, the chip pad size must be reduced and the interval between inner leads must be reduced, which results in a lead frame having a fine pitch.
In order to fabricate such a fine pitch type lead frame, known fabrication methods have required a new stamping tool punch for a stamping tool in order to fabricate the inner leads. Undesirable amounts of time and money are required to design and fabricate such a stamping tool punch.